1. Field of the Invention
This invention is related generally to remote devices which are components of a three-phase power distribution network communication system, and more specifically, to improved sampling circuits for such remote devices.
2. Description of the Prior Art
Considerable effort has been devoted in recent years to develop power distribution network carrier communication systems due to the increased desirability of performing certain automated functions, such as the automatic reading of utility meters, selective load control, performing load continuity checks, and the like. U.S. Pat. Nos. 3,967,264; 3,942,168; and 3,911,415 and U.S. patent application Ser. No. 252,682 filed Apr. 9, 1981, all assigned to the assignee of the present invention, disclose some form of communication system via the power distribution network of an electric utility. The communication systems disclosed in the aforementioned patents and patent application allow an electric utility to communicate with a variety of remote devices by using the power distribution network for carrying the communication signal.
It is known in the prior art that in situations where multi-conductor service is provided to customer locations, the performance and reliability of the communication system may be improved by using each of the phase conductors as a communication path. In these types of communication systems, each of the phase conductors carries an identical communication signal. Examples of power distribution network communication systems having a communication signal coupled to each of the phase conductors are U.S. Pat. No. 4,065,763; U.S. patent application Ser. No. 252,681 filed Apr. 9, 1981 which are both assigned to the same assignee as the present invention, and U.S. Pat. No. 4,188,619.
Although the coupling of the communication signal to each of the phase conductors improves the reliability and performance of the communication system, it increases the complexity of the receiving remote devices since the remote devices must now be responsive to more than one communication signal. This has caused problems in devices such as signal repeaters which are coupled to each of the three-phase conductors. Microprocessor-based signal repeaters which could receive and process a single communication signal must now receive and process three identical communication signals. In many applications, it has been discovered that the time required for sampling and reconstructing each of the communication signals is so long that the microprocessor-based remote device does not have sufficient time for processing the received signals. This problem has led design engineers to use larger or faster microprocessors which causes both the complexity and the price of the remote devices to increase.